In the case of the current radio access network, it is usual that a base station always operates, and sending output of a pilot channel or the like is kept constant. Accordingly, for example, in the case that no mobile station exists or a small number of mobile stations exist in a cover area of the base station, electric power is consumed wastefully. Meanwhile, in order to cope with the environmental problem which invades on the global scale, it is desired to construct a wireless access network which uses a small amount of electric power consumption.
As an art to realize the desire, arts described in a patent document 1 and a patent document 2 are exemplified. The patent document 1 discloses a method shown in the following. That is, one base station measures electric power of a receiving signal from a surrounding base station which surrounds the base station, and an amount of traffic of the surrounding base station. In the case that an amount of the traffic of the surrounding base station is small, and the electric power of the receiving signal satisfies required quality, the base station lowers electric power of a sending signal in response to a load of the base station and stops sending the signal finally. Moreover, the patent document 2 discloses a method to strengthen sending power of one central base station, and to make a base station, which is adjacent to the central base station, stop sending a signal and to make the adjacent base station enter into a state of receiving a signal, and consequently to make power consumption of a whole of a system decreasing, when an amount of traffic becomes decreasing.